The invention relates to a torque transfer system for a motor vehicle, a method of operating the torque transfer system, and a method of operating the motor vehicle that comprises utilizing the torque transfer system.
A torque transfer system in the particular context of the present invention means an arrangement or system that includes a clutch device and/or a torque converter device and/or a transmission. The torque transfer system has at least one input shaft and one output shaft, where the rotary transfer quantities carried through the input shaft and the output shaft may be equal or different in magnitude.
A rotary transfer quantity within the present context means a torque or a rate of rotation (rpm rate, for short). A torque transfer system of the kind that the present invention aims to improve is preferably configured so that it can at least part of the time uncouple at least one input shaft and at least one output shaft from each other.
As a matter of terminology, it should be noted that the term xe2x80x9ctorque-transmitting devicexe2x80x9d, which will also be used herein, has a different meaning from xe2x80x9ctorque transfer systemxe2x80x9d. The torque transfer system proposed by the present invention preferably includes a torque-transmitting device as a component.
The term xe2x80x9cclutch devicexe2x80x9d as used herein refers to a device that includes a clutch that can be engaged and disengaged, such as a friction clutch and/or a start-up clutch and/or a reverse-gear clutch and/or a laminar disc clutch and/or a magnet powder clutch and/or a converter bypass clutch. With particular preference, the clutch device is configured as an automated clutch device of the kind which the assignee of the present invention describes and offers for sale under the name xe2x80x9cElectronic Clutch Managementxe2x80x9d (ECM).
A transmission device in the particular context of the present invention means a device by which different transmission ratios can be set. The selection of transmission ratios may be either continuous, i.e., without steps, or it may have a finite number of discrete levels or steps. Examples of transmission devices envisaged here include manual shift transmissions, multi-step transmissions, cone-pulley transmissions and the like. In particular, the transmission device consists of an automatic transmission, preferably of the type that uses a planetary gear mechanism and can be shifted without interrupting wheel traction. As an alternative, the transmission device may also be an automated shift transmission. The term xe2x80x9cautomated shift transmissionxe2x80x9d as used herein means a transmission with a gear layout analogous to a manual transmission with the addition of automated controls for at least a part of the shift movements, and in particular for all of the shift movements. An actuating device is provided for the automated controlling of the shift movements, including in particular a hydraulic device with a piston/cylinder arrangement and/or at least one electric motor.
In the context of the present invention, the terms xe2x80x9ctorque transfer systemxe2x80x9d, xe2x80x9cclutch devicexe2x80x9d as well as xe2x80x9ctransmission devicexe2x80x9d also include combinations of the aforementioned representative embodiments of the different devices.
The known state of the art already includes torque transfer systems with an automated clutch device and a transmission device in which the respective shift movements of the clutch device and the transmission device are performed in coordination with each other. Devices of this kind are known in particular for the automated movement of the clutch. Although these known devices are already proven in practical use, it would seem desirable to develop them further to make them more adaptable and more flexible for certain operating states and traction load states of a motor vehicle.
The terms xe2x80x9ctraction loadxe2x80x9d and xe2x80x9ctraction load statexe2x80x9d in the context of the present invention refers in particular to extraneous factors of the vehicle, e.g., the position and orientation of the vehicle on a road surface, which may increase the driving resistance in relation to a predetermined reference resistance in at least one driving direction. Of particular interest in the present context are situations that lead to an increase in driving resistance dependent on the direction of travel.
A reference resistance in the present context means a specific amount of driving resistance encountered by the motor vehicle when traveling on a level surface at normal atmospheric pressure, with a normal air drag coefficient (Cd) of the vehicle without accessory structures such as a rooftop carrier or a trailer or the like, and at a specified total weight defined specifically as 75 kilograms above the weight of the empty vehicle.
Some traction load states considered in the context of the present invention relate to conditions where the driving resistance is higher than under the aforementioned normal reference conditions. An increased driving resistance may be due to the fact that the vehicle is traveling up an incline or that the vehicle is pulling a trailer.
The invention therefore has the object of providing a torque transfer system for a motor vehicle as well as a method of operating the torque transfer system, offering a cost-effective and technically simple solution for performing rapid and precise shift movements adapted to traction load conditions of the vehicle, leading to a higher level of driving comfort.
The proposed solution according to the invention is to provide a torque transfer system for a motor vehicle with a control device that is at least part of the time connected to a traction-load detecting device with at least one sensor device to determine the traction load of the vehicle.
The torque transfer system, which specifically includes a clutch device and a transmission device, is appropriately configured so that it can be arranged in the power train of a motor vehicle between an input shaft and an output shaft.
The term xe2x80x9cdrive sourcexe2x80x9d in the present context means in particular a motor or a combustion engine or the like. The terms xe2x80x9cdownstream sidexe2x80x9d or xe2x80x9coutput sidexe2x80x9d refer to a shaft that is arranged in the power train between the transmission device and the wheels of the vehicle. It should be noted that a vehicle with a torque transfer system according to the invention may also be set in motion with a torque flowing in the upstream direction of the power train. This can particularly be the case, if a vehicle parked on an incline is set into motion by disengaging the transmission lock and/or the clutch without depressing the accelerator pedal, i.e., by using the downhill component of the gravity force.
The torque transfer system can be shifted between different operating states that affect the ratio between the rotary transfer quantities. In particular, a clutch device that is part of the torque transfer system may be taken out of engagement, so that the input shaft and the output shaft are essentially uncoupled from each other. On the other hand, the clutch device may also be shifted into complete engagement so that, with the transmission in gear, the input shaft and the output shaft are positively coupled to each other. Further according to the invention, the clutch device is designed so that it can operate in a state where a predetermined amount of torque is transmitted through the clutch device.
In particular, the transmission device is designed to operate with two or more different transmission ratios.
The control device can set the torque transfer system into the different operating states according to a predetermined characteristic relationship.
A control device in the sense of the present invention specifically has the capability to engage the clutch device to a degree where the vehicle is moved in a crawl mode.
A crawl mode in the present context means that the vehicle is moving at a slow speed with a gear engaged, with the engine running, and without applying the brakes. The amount of torque transmitted through the clutch device in this operating state is small. In particular, according to the invention, the torque that the clutch device is allowed to transmit is limited to a predetermined small amount.
The present invention further provides that the control device is designed to manage a start-up phase of the vehicle from a stand-still condition. In a start-up phase, an engine-load control lever, usually a gas pedal, is actuated by the driver so that the drive source runs at a higher rpm rate than the idling speed, and at least a small amount of clutch engagement causes the vehicle to slowly begin to move.
In particular, the invention provides that the control device regulates the crawl movement and/or start/up movement of the vehicle in accordance with a predetermined characteristic relationship that may be defined through mathematical functions, data arrays, curve fields or the like.
A traction load sensor device in the present context means a device with at least one sensor.
As a preferred arrangement, the traction load sensor device detects or monitors the value of a characteristic quantity of a kind that allows the traction load detecting device or the control device to determine the traction load state of a vehicle without resorting to a comparison or comparative mathematical evaluation of operating quantities of the input and output ends of the power train. In particular, the invention calls for a sensor device that can detect the traction load independent of a comparison of vehicle accelerations which, in turn, are based on the engine torque and on at least one wheel rpm rate. Nevertheless, this approach is not excluded under the invention as a way to determine the traction load of the vehicle.
According to the invention, a control device is at least part of the time connected to a traction load detecting device through an analog or digital data connection and is equipped to generate a signal that is a function of the traction load state of the vehicle and allows a determination of the traction load of the vehicle independent of a comparison or, in particular, a comparative mathematical analysis of operating quantities at the engine side and the wheel side of the power train.
With the aforementioned analog or digital connection between the control device and the traction load detecting device, the connected devices can be spatially separated from each other, or one of the devices could be part of the other. The data transmission from one device to the other may be implemented through a wireless connection or through a cable or other conducting element. The signal that is transmitted through the connection may be a variable analog signal or a discrete signal. Also among the preferred solutions, the transmitted information may be in the form of a digital signal. In particular, a digital signal may indicate whether the traction load is at the reference level or at an increased level.
A traction load detecting device in the sense of the present invention may in particular include an inclination angle detecting device. The latter may produce a sensor signal that is a function of the angle at which the vehicle is inclined in relation to a horizontally leveled position.
An inclined vehicle position in the present context means in particular that the vehicle is inclined lengthwise or side-to-side or in both directions in relation to a level plane.
As a preferred concept of the invention, at least one characteristic value of the driving properties of the vehicle and/or the torque transfer system is controlled by the traction load detecting device and/or the control device and/or the inclination angle detecting device in accordance with a predetermined characteristic.
With preference, the traction load sensing device is arranged substantially on the transmission device and/or the control device.
Preferably, the traction load sensing device has a sensor arrangement with at least one sensor in the fuel tank of the motor vehicle. There are preferably two sensors, and with particular preference three sensors, arranged in the fuel tank of the vehicle.
One preferred use for this sensor arrangement or of the at least one sensor is to detect the fill level of the fuel in the tank.
In accordance with a highly preferred embodiment of the invention, the sensor arrangement in the fuel tank can serve at least part of the time to detect the shifts in the position of the fuel, preferably through a high-frequency detection principle, and to generate an inclination angle signal. In particular, a sensor arrangement of this type can detect the position changes of the fuel in the tank when the vehicle travels uphill or downhill, in comparison to the condition of the fuel when the vehicle travels on a level surface. It is particularly preferred, if the sensor arrangement also detects the direction of the change in position of the fuel.
A inclination-angle signal, which is a function of the information collected by the sensor arrangement, is transmitted to the control device.
According to a particularly preferred embodiment of the invention, the signals detected by the tank sensor arrangement, which are representative of the tank fill level, are evaluated by the control device for different time windows of different lengths. From the change in the fill level within the time windows, or from a comparison of fill levels of at least two time windows, and/or from a comparison of the time gradients of the fill level within different time windows, the control device determines if and by how much the fuel volume in the tank has changed and/or whether the inclination angle of the vehicle has changed, or the amount of the inclination angle at which the vehicle is currently positioned.
The term xe2x80x9ctime windowxe2x80x9d in the present context means a time period of predetermined length, or which begins at a predetermined point in time, particularly controlled by the occurrence of an event, and/or ends at a point in time that is controlled by an event.
Preferably, three time windows are used for the data evaluation, with a first time window extending over a long time period, a second time window extending over a mid-sized time period, and a third time window extending over a very short time period.
Under a particular concept of the invention, the time windows under evaluation run at least in part concurrently. Preferably, the third time window is contained within the second window, and the second window is contained within the first window.
In particular, the evaluation of the change in fill level detected during the first time window can be used to determine a change in the fuel volume in the tank. The change in fill level registered during the second time window can be used in particular to determine a change in the inclination angle of the vehicle. The change in fill level detected during the third time window is preferably used as an indicator of a short-term irregularity. A particular example of a short-term irregularity occurs when the vehicle encounters a pothole in the pavement.
As a preferred concept of the invention, the evaluation of the time windows further involves characteristic operational quantities of the vehicle such as the gas pedal position, or the gear being used in the transmission, or the transmittable amount of torque through the clutch, or the engine torque, or the engine rpm rate, or other data, which are evaluated in accordance with a predetermined characteristic.
According to a particularly preferred embodiment of the invention, a fuel tank sensor is arranged in the middle of the tank. Preferred arrangements further include a tank sensor at an out-of-center location of the tank, or two sensors, one of which is located at the center and the other is located out of the center. With particular preference, the second tank sensor is offset from the center of the tank in the lengthwise direction of the vehicle. Other preferred arrangements include one tank sensor in a corner of the tank, or two tank sensors in diagonally opposite corners of the tank, or two tank sensors in different corners of the tank, or two tank sensors in opposite corners of the tank in relation to the transverse direction of the vehicle. With particular preference, one tank sensor is arranged at the center of the tank, while two further tank sensors are arranged at opposite corners of the tank in relation to the transverse direction of the vehicle. Also with particular preference, at least one tank sensor is arranged in the proximity of a wall of the tank.
Preferably, one or more tank sensors, and with the highest preference all of the tank sensors, are arranged so that they can detect the fill level all the way to the point where the tank is empty.
In the present context, the middle or center of the fuel tank means in particular the area center of gravity of a horizontal cross-section through the tank, i.e., of the area that is delimited by the intersection of the imaginary cross-sectional plane with the walls of the tank. The foregoing references to the corners of the fuel tank are specifically meant as the corners of the imaginary cross-sectional area.
According to a particularly preferred embodiment of the invention, the control device determines the inclination of the vehicle on the basis of the differences in the fill heights that are detected by different sensors at the same point in time. It is particularly preferred if the sensors are arranged so that the lengthwise inclination of the vehicle can be determined. Preferred embodiments of the invention further include sensor arrangements by which the transverse inclination can be detected as well as arrangements by which both the lengthwise and transverse inclination of the vehicle can be determined.
With preference, the traction load sensor arrangement includes at least one acceleration sensor arrangement.
An example of an acceleration sensor is represented by a collision sensor, also known as crash sensor. The term xe2x80x9ccrash sensorxe2x80x9d relates in particular to sensors or sensor devices that can be used in motor vehicles to trigger the deployment of an air bag or other safety devices.
Preferably, the acceleration sensor detects the actual vehicle acceleration, particularly in terms of absolute amounts of acceleration. As a preferred concept, the acceleration sensor is designed to provide acceleration data also when the vehicle is standing still, if an acceleration is present. For example, a sensor for detecting acceleration in the traveling direction would also indicate an acceleration if the longitudinal axis of the vehicle is inclined in relation to a level plane. This situation applies when the vehicle is standing still on an uphill or downhill grade. The reason why the acceleration sensor registers an acceleration is that the vector of the gravitational force has a component in the lengthwise direction of the vehicle. The effective acceleration in the lengthwise direction of the vehicle is in essence represented by gxc3x97sin xcex1, where xcex1 represents the angle of lengthwise inclination of the vehicle in relation to a horizontal plane and g represents the acceleration due to gravity.
With preference, the control device determines the inclination of the vehicle at least part of the time from changes in vehicle acceleration, particularly from the absolute amounts of acceleration as determined by the traction load sensing device.
According to a particularly preferred embodiment of the invention, the grade angle of the pavement on which the vehicle is traveling is determined on the basis of the time profile of the acceleration values detected by the acceleration sensor. The inclination of the vehicle can be determined in particular on the basis of the acceleration values generated by an acceleration sensor in combination with at least one further characteristic operational quantity such as, e.g., the wheel rpm rate of the vehicle.
The invention further proposes the concept that a control device controls the torque transfer system dependent on a signal that is transmitted from a traction load detecting device to an optical device.
The traction load detecting device is generally of a type as described herein. However, the traction load detecting device may also work in any other possible manner to generate a signal that is representative of the traction load.
An optical device in the present context means in particular a device that provides an optical indication of a specific traction load condition. This includes in particular a blinking light that is arranged in the display panel of the vehicle and operated by a control device, or a control light for the presence of a trailer, or other luminous indicators.
With preference, the signal transmitted to the optical device is used for the selection of a shift program and/or a clutch-engagement/disengagement characteristic, or for the control of the start-up rpm rate, or to effect a change in the crawl torque.
In particular, the invention proposes to increase the start-up rpm rate if the presence of a trailer has been detected and/or to adjust the crawl torque to a higher traction load which may be caused by a trailer or other factors.
Among the preferred possibilities, the signal transmitted to the optical device, preferably an electrical signal, is present only when the vehicle is connected to a trailer.
According to the invention, the clutch device that is part of a torque transfer system is under certain conditions partially retracted from engagement as a result of a control signal of the sensor device. The control signal depends on a predetermined characteristic operating value that is controlled according to a predetermined characteristic. The clutch device is taken out of engagement in particular when the characteristic operating value reaches a predetermined threshold.
According to the invention, the predetermined threshold of the characteristic operating value depends in particular on the signal generated by the traction load detecting device in accordance with a predetermined characteristic.
According to the invention, the characteristic operating value can be the engine rpm rate and/or the transmission rpm rate of a motor vehicle. Specifically, the invention proposes the concept of disengaging the clutch at a transmission rpm rate of, e.g., 1000 rpm under predetermined conditions while the vehicle is traveling on a level road without a trailer. If the vehicle is traveling on a downhill grade, the transmission rpm rate at which the clutch is disengaged is preferably set at a lower value dependent on the detected traction load state.
As a notable feature of the invention, the clutch device is controlled by the control device preferably in a such manner that the amount of torque that is transmittable through the clutch is immediately reduced if the transmission rpm rate falls to a predetermined level, known as the clutch-disengagement threshold. By reducing the amount of torque carried through the clutch, the latter will be put into a slipping state, so that the transmission rpm rate and the engine rpm rate will increasingly diverge. As a consequence, in a situation where the vehicle is traveling downhill, the transmission rpm rate may increase because of the torque entering the power train from the output side, while the engine rpm rate changes towards the idling rpm rate, i.e., decreases. At the point where the transmission rpm rate has risen to a predetermined value, which may be set at 1200 rpm, the clutch device is controlled according to another subroutine of the control characteristic. As a preferred possibility for this control phase, the target value for the transmittable clutch torque, which prior to that point was regulated at a constant level, is now controlled by setting separate targets for the portions allocated to slippage and to driving the vehicle. As a result of this control, the target torque value for the transmittable torque is strongly increased. This will cause the transmission rpm rate to decrease and, at least after a certain time, it will cause the gap between the engine rpm rate and the transmission rpm rate to become increasingly smaller, until the two rpm rates are synchronized again.
The rpm threshold at which the clutch disengagement is initiated and thus the level of transmittable torque is drastically reduced, is set for example at 1000 rpm for an operating situation where the vehicle is traveling on level ground. If it has been detected that the vehicle is traveling on a downward grade, this value is set lower. For example in Diesel vehicles, the threshold is reduced to a value that is 100 rpm above the idling rpm rate.
The foregoing feature of the invention is advantageous in that an early disengagement of the clutch, i.e., disengaging the clutch at a higher rpm rate, is beneficial to the driving comfort of the vehicle. Particularly with a strong application of the brakes when traveling on level ground, an early disengagement of the clutch prevents stalling of the engine.
However, when traveling on a downhill grade, an early disengagement of the clutch has the consequence that the vehicle will be rapidly accelerated by gravity to a speed where the transmission rpm rate will again reach 1200 rpm, where the clutch will re-engage. The time interval where traction is interrupted may in this case be too short, for example to shift gear.
By reducing the rpm threshold for clutch disengagement, the time period between the disengagement and re-engagement of the clutch can be made longer, which in particular makes gear-shifting more comfortable.
The invention also provides measures to avoid a cyclic alternation between engagement and disengagement of the clutch when traveling along a downhill grade.
Preferably, the transmission device can additionally be controlled by the driver of the vehicle through a selector lever which allows the driver, e.g., to set a mountain-driving gear. As a particularly preferred feature, the setting of the mountain-driving gear will generate a signal to the control device to select a different characteristic for controlling the clutch.
According to a particularly preferred embodiment of the invention, the traction load detecting device can generate a signal that indicates whether the vehicle is connected to a trailer.
Further according to the invention, the control device may control certain designated operating quantities of the vehicle and/or of a drive source of the vehicle and/or of the torque transfer system in accordance with a predetermined characteristic and based on the signal generated by the traction load detection device.
With preference, the start-up rpm rate of the motor vehicle is controlled as a function of the traction load.
The start-up rpm rate in the present context is defined in particular as the controlled rpm rate during the start-up phase.
A start-up phase in the sense of the present context is in particular a process in which an engine-load control lever such as a gas pedal is being actuated, where the engine rpm rate is in essence above the idling rpm rate and the vehicle is starting to move at least slowly as the clutch is engaged at least to a minor extent.
According to a particularly preferred embodiment of the invention, the control device under certain conditions regulates the clutch device in such a manner that the latter transmits a crawl torque of a magnitude that depends on a signal generated by the traction load detecting device.
It should be noted that a crawl torque in the present context is defined as a torque of small magnitude, which can be transmitted by the clutch device when the vehicle engine is running and neither the brake nor the gas pedal are being applied by the driver.
According to a particularly preferred embodiment of the invention, the control device will cause the crawl torque to increase if the signal generated by the traction load detecting device indicates certain predetermined traction load conditions. One such traction load condition may be the fact that a trailer is connected to the vehicle, or that the traction load caused by the trailer exceeds a given traction load limit, or that a certain grade angle is exceeded, or any other condition that affects the traction load on the vehicle.
According to a particularly preferred embodiment of the invention, the control device will initiate a predetermined driving program in response to a signal generated by the traction load detecting device. A driving program in this particular context consists of a given characteristic functional relationship according to which the torque transfer system or, more specifically, the transmission device and the clutch device are controlled.
By selecting a driving program that depends on the traction load condition of the vehicle, it is possible to provide a variable clutch engagement/disengagement characteristic and/or a variable gear-shifting characteristic, or other variations in automated functions of the torque transfer system.
In particular, the invention proposes a more rapid engagement of the clutch under conditions of increased traction load, i.e., especially with an increased gross vehicle weight or, in other words, with a heavy load, or when the vehicle is pulling a trailer.
This can be particularly advantageous for heavy vehicles or vehicles pulling a trailer, because the larger weight can have the consequence that a larger amount of energy is absorbed in the clutch, i.e., converted into heat. It is therefore desirable to reduce this energy dissipation, and one way to achieve this is by shortening the periods of clutch slippage through a more rapid re-engagement of the clutch.
According to a concept of the invention, the traction load condition of a vehicle is registered over a longer time period, and the registered data are subsequently evaluated. Based on the evaluation, a characteristic profile is determined, based on which traction load conditions can subsequently be predicted or can be detected more rapidly when they occur.
The evaluation results can, e.g., be made available when the ignition is switched on.
Also included under the scope of the invention is any process or method of operating a vehicle that makes use of the inventive torque transfer system or of the inventive methods and programs employed in the torque transfer system.
As a linguistic formality, where the names of features are connected by the word xe2x80x9corxe2x80x9d, this should be understood in the broadest sense, i.e., either as a logic type of or (one or the other or both) or an exclusive or (one or the other but not both), whichever fits the context.
The terms xe2x80x9ccontrolxe2x80x9d and xe2x80x9cregulationxe2x80x9d and their derivatives are used herein with a broad range of meanings encompassing closed-loop as well as open-loop control of devices, functions and processes, including in particular the DIN (Deutsche Industrie-Norm) definitions for regulation and/or control).
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.